Performance problem with drawing circles

[kamre]

If you want a fast an advanced canvas with zoom:

Use QGraphicsView.

This is not possible for me because there is a limitation:

QGraphicsItem does not support use of cosmetic pens with a non-zero width.

And I need to draw my shapes with pen width that is the same for all zoom levels. So painting bounds for shapes are different for different zoom levels and QGraphicsView can't handle such cases, am I right?

In any case I'll try to reproduce this behaviour with QGraphicsView, cause I think the problem is somewhere in QPainter.

[kamre]

By the way here is a Java2D implementation (just rename the attachment to jar) and there is no such problem with performance as in Qt. So what is wrong with my approach to zooming in Qt version?

[kamre]

I have run this simple example with callgring profiler and here are the results.

When zoom level is not big and everything is rather fast:


With big zoom level and degraded performance:


So the problem begins with the call of function QPainter::intersected.
What is wrong in my example? Is this a known Qt4 limitation/feature or bug?